The present invention relates to plasma display devices.
A plasma display device is comprised of a body of ionizable gas sealed within a nonconductive, usually transparent, envelope. Alphanumerics, pictures and other graphical data are displayed by controllably initiating and quenching glow discharges at selected locations within the display gas. This is accomplished by establishing electric fields within the gas by way of appropriately arranged electrodes, or conductors.
The present invention more particularly relates to so-called ac plasma panels in which the electrodes are insulated from the display gas. There are two basic types of ac plasma panels, twin substrate and single substrate. As described, for example, in U.S. Pat. No. 3,499,167 issued Mar. 30, 1970 to T. C. Baker et al, the former have electrodes embedded within dielectric layers disposed on two opposing nonconductive surfaces, or substrates, such as glass plates. Most commonly, the electrodes are arranged in rows on one substrate and columns orthogonal thereto on the other. The overlappings, or crosspoints, of the row and column electrodes define a matrix of display sites, or cells. Each display site can be individually switched between ON (energized, light-emitting) and OFF (de-energized, non-light-emitting) states in response to voltages applied between its electrode pair. Other twin substrate electrode arrangements, e.g., multiple segment characters, are possible.
Single substrate ac plasma panels, by contrast, have all electrodes disposed on a single one of the surfaces. As taught, for example, in my U.S. Pat. No. 3,935,494 issued Jan. 27, 1976, the electrodes may be located at different levels within the dielectric layer disposed on that one surface. With this "nonplanar" geometry, glow discharges are initiated in response to fringing fields appearing in the gas in the general region of overlapping insulated electrode pairs. Alternatively, as taught, for example, in U.S. Pat. No. 3,811,061 issued May 14, 1974 to N. Nakayama et al, electrodes of various geometries may be positioned at a single level, or plane, within the dielectric. With this "planar" geometry, discharges occur in response to fields appearing in the gas in the general region of neighboring pairs of electrodes.
More particularly, the Nakayama patent discloses a planar ac plasma panel in which row and column conductors are located at lower and upper levels, respectively, within the dielectric layer (the designations "row" and "column" being, of course, arbitrary). Conductive pads, arranged in rows and columns, are embedded in the dielectric layer at the upper level to provide a row and column array of display sites. Addressing, e.g., write and erase, signals on each lower level, row conductor are extended to the associated pads thereabove by way of ohmic, i.e., substantially resistive, paths in the form of so-called conductive vias. Disadvantageously, the inclusion of vias in the design of the panel renders the fabrication process substantially more complicated than is required for nonplanar panels, for example. In addition, the nature of the via fabrication steps tends to make uniform panel characteristics more difficult to achieve.